1. Field of the Invention
The present invention relates to rotary drum filters used in the manufacture of pulp in the paper making process, and more particularly to a hollow trunnion with a replaceable packing sleeve insert for such a filter.
2. Description of the Prior Art
In known rotary drum filters, the filter drum has a hollow trunnion, usually made of mild steel. The inner wall of such trunnion is lined throughout its length with an abrasion- and chemically-resistant material, such as stainless steel, for withstanding the abrasion of its packing seal and the chemical action of the filtrate which passes through the trunnion. When this lining wears out, as it always does sooner or later, either the entire trunnion or its lining must be replaced. If the latter course is chosen, the original lining must be laboriously cut out in its entirety and replaced with a new one, which also eventually wears out, so that the repair must be repeated. Either alternative is expensive because of the high replacement cost of a new trunnion, and because the relining process is labor-intensive. Both alternatives also require that the entire paper production line be shut down for a considerable period of time while the faulty filter drum is removed from the line and replaced with another one, or while the drum is repaired on line. In either case, considerable production time is lost, and the additional expense of installing a replacement drum while repairs are made will be self-evident.
Thus, there is a need for a better hollow trunnion for rotary drum filters which is more wear-resistant and which can be more easily repaired, preferably on-line, when its lining needs replacement because of wear or chemical action.